We will continue a multilevel approach to the study of cell function in terms of membranes and organelles. We find, in diabetic animals, altered enzymic characteristics of D-Beta-hydroxybutyrate dehydrogenase (BDH), a lipid-requiring enzyme which has been related to altered fatty acid composition of phospholipid in the mitochondrial membrane. This finding portends a new dimension to the disease process. Hence, a major program is planned on the level of the whole animal to study the affect of metabolic changes and the disease state on the composition and functional characteristics of subcellular organelles and membranes of rat liver. We will compare normal, diabetic, and starved animals and attempt to relate specific effects of glucagon and insulin. Another program is the study of muscle membranes with regard to understanding muscle physiology especially excitation-contraction coupling. We will continue studies of sarcoplasmic reticulum (SR), a biological pump capable of energized CA ions transport important in muscle physiology. Experiments are ongoing to obtain the molecular architecture of this membrane and relate its structure to function. The reconstitution approach is being used to prepare membranes of defined lipid-protein composition and of defined lipid environment. Reconstituted functional membranes (R-SR) can be prepared with wide variation in phospholipid content. Most important for the study of lipid-protein interaction is that we can prepare membranes with lipid content similar to the original membrane both higher and lower by a factor of two. Such R-SR composed mainly of one protein component i.e., the calcium pump protein and phospholipid represents a simplified segment of the membrane. We will continue our studies of BDH a lipid-requiring enzyme to understand the nature of lipid-protein interaction and the basis of the role of lipid. For these two simplified membrane systems i.e., R-SR and BDH-phospholipid complex, a variety of biophysical techniques including X-ray and neutron diffraction, and NMR will be used to obtain detailed molecular structure of the membrane, including motional parameters and the nature of lipid-protein interaction.